[Python-3000] C API for ints and strings

["Martin v. Löwis"]

> Hm, then perhaps rangeobject.c shouldn't use it?

That use is correct also; the int_range_iter is also an
optimization. It does not matter that the result is not correct;
if one bound is >2**30, it will create a longrangeiter, even though
an int one would still be sufficient.

Regards,
Martin